Control of Haemophilus parasuis in Pigs

In recent years, with the invasion of immunosuppressive diseases such as blue ear disease and circovirus disease to varying degrees, and the "aiding evil" of mycoplasma disease, another immunosuppressive disease in most pig farms, the immunity and resistance of pigs have been seriously reduced, and the phenomenon of mixed infection of the disease is very common. In the technical service, we found that Haemophilus suis often appeared as a secondary and concurrent infection in the nursery and growth house of some pig farms, which greatly increased the death rate of pigs and caused huge losses to pig farms. Let's talk about the understanding and control methods of the disease for colleagues' reference.

1 some main characteristics of Haemophilus parasuis in pigs

1.1 Haemophilus parasuis in pigs is also known as polyfibrinous serositis and arthritis, also known as gram's disease. Haemophilus parahaemophilus belongs to Gram-negative Brevibacterium, with more than 15 serotypes, of which serotypes 5, 4 and 13 are the most common (more than 70%).

1.2 the growth of the strain strictly requires nicotinamide adenine dinucleotide, so it is difficult to isolate and culture under general conditions, especially in the treatment of diseased pigs with antibiotics, which brings difficulties to the diagnosis of the disease. It is reported that the true incidence of Haemophilus parasuis in pigs may be as much as 10 times that of actual diagnosis.

1.3 the bacteria belongs to conditional bacteria, and the disease occurs frequently when the feeding environment is bad. Weaning, switching, mixing or transportation are also common causes.

2 some current manifestations of Haemophilus parasuis in pigs

2.1 Haemophilus parasuis only infects pigs, which can affect young pigs from 2 weeks to 4 months of age, mainly before and after weaning and during the conservation stage. It is commonly seen in 5-8-week-old pigs, with an incidence of 10%-15% and a mortality rate of 50% in severe cases.

2.2 Acute cases often occur first in pigs with good body condition, fever (40.5 ℃ ~ 42.0 ℃), depression of spirit, loss of appetite, dyspnea, abdominal breathing, redness or pallor of the skin, purple tip of the ears, subcutaneous edema of the eyelids, slow walking or reluctance to stand, enlargement of the wrist and tarsal joints, ataxia, lying on the side or limbs before death. Sometimes he dies suddenly without obvious symptoms.

2.3 chronic cases are most common in nursing pigs, mainly loss of appetite, cough, dyspnea, rough coat, weakness or claudication of limbs, poor growth until failure and death.

Other respiratory diseases, such as mycoplasma pneumonia, porcine reproductive and respiratory syndrome, circovirus disease, swine influenza, pseudorabies and porcine respiratory coronavirus infection, will increase the risk of Haemophilus suis and aggravate the clinical manifestations of PMWS (postweaning multisystemic wasting syndrome of piglets) in nursing homes during production.

(3) Analysis of the causes of disease epidemic.

In pneumonia, Haemophilus suis is assumed to be a secondary pathogen of random invasion, an "opportunistic" pathogen that causes disease only in conjunction with other viruses or bacteria. In recent years, the rate of Haemophilus parasuis isolated from pigs with pneumonia is getting higher and higher, which is related to the increasing prevalence of mycoplasma pneumonia and viral pneumonia. These viruses mainly include porcine reproductive and respiratory syndrome virus, circovirus, swine influenza virus and porcine respiratory coronavirus. Haemophilus parasuis combined with mycoplasma, the detection rate of pig lungs with PRRS (porcine reproductive and respiratory syndrome) was 51.2%.

4 Prevention and treatment of Haemophilus parasuis in pigs

4.1 Drug sensitivity tests of sensitive drugs of Haemophilus parasuis are rarely reported in China, but from the perspective of practical application, florfenicol, cephalosporins, amoxicillin, ampicillin, quinolones, gentamicin and synergistic sulfonamides have certain therapeutic effects, and most strains are resistant to erythromycin, aminoglycosides and lincomycin.

4.2 main points of prevention and treatment of Haemophilus parasuis in pigs

4.2.1 the effect of antibiotics in the treatment of severe Haemophilus parasuis is not satisfactory. once the clinical symptoms have appeared, the infected pigs should be injected with large doses of the above-mentioned sensitive antibiotics every 6 to 8 hours. At the same time, the whole herd of other pigs should be prevented.

4.2.2 the therapeutic effect of the disease is not good. In the production practice of pig farms, it is the best policy to prevent the outbreak of the disease, because the disease usually occurs as a secondary or concurrent infection, often accompanied by mixed infection of mycoplasma. Adding scientific drug combination to feed is an important means to prevent the disease. For example, 100 mg / kg of Zhiyuanjing + 300 mg / kg of chlortetracycline + 250 mg / kg of amoxicillin or 100 mg / kg of Zhiyuan Jing + 80 mg / kg of florfenicol were added to the feed of piglets after weaning.

4.2.3 immunity: in pig farms where Haemophilus parasuis is serious, pigs can be immunized if necessary, because there are many serotypes of the disease and the effect of commercial vaccine is uncertain, their own vaccine has a certain preventive effect; those without conditions can also be immunized with multivalent inactivated vaccine of Haemophilus parasuis; first immunity in 40 days before delivery and two immunity in 20 days before delivery. Immunized pigs can be immunized once 30 days before delivery. Piglets in pig farms seriously threatened by the disease should also be immunized, and the immunization time should be inferred according to the age of onset in the pig farm. The immunization of piglets is generally arranged within 7 days of age to 30 days of age, with 1 ml each time. It is best to repeat immunization 15 days after the first immunization, and there should be an interval of more than 10 days between the second immunity and the onset time.

4.2.4 eliminate inducement, strengthen feeding management and environmental disinfection, reduce all kinds of stress, do not mix piglets temporarily when weaning piglets in pig farms with conditions during the epidemic of the disease, strictly control mixed pigs, isolate diseased pigs in the same pig house, and "graded feeding" of weaned pigs, which can also reduce the spread of porcine reproductive and respiratory syndrome and circovirus disease in pigs. Pay attention to the change of heat preservation and temperature difference. Some anti-stress drugs such as vitamin C can be added to drinking water before and after weaning, herding, mixing or transportation, and the above recommended drug combination can effectively prevent the occurrence of the disease. The effective prevention and control of Haemophilus parasuis in pigs, like the prevention and treatment of any other diseases in pig farms, is a systematic project. it is necessary for us to strengthen the immunity of major viral diseases, select effective drug combinations for routine prevention and health care of pigs, improve pig feeding and management, and redesign pig houses.